Voltage Regulation Planning for Distribution Networks Using Multi-Scenario Three-Phase Optimal Power Flow

Abstract

Active distribution networks must operate properly for different scenarios of load levels and distributed generation. An important operational requirement is to maintain the voltage profile within standard operating limits. To do this, this paper proposed a Multi-Scenario Three-Phase Optimal Power Flow (MTOPF) that plans the voltage regulation of unbalance and active distribution networks considering typical scenarios of operation. This MTOPF finds viable operation points by the optimal adjustments of voltage regulator taps and distribution transformer taps. The differentiating characteristic of this formulation is that in addition to the traditional tuning of voltage regulator taps of an active network applied for just one scenario of load and generation, it also performs the optimal adjustment of distribution transformer taps, which, once fixed, is able to meet the voltage limits of diverse operating situations. The optimization problem was solved by the primal-dual interior-point method and the formulation was tested using the IEEE 123-bus system.Energies 2020, 13, 159 2 of 21 Thus, this research adjusted a single-period Three-Phase Optimal Power Flow (TOPF), proposed by the authors of [1], into a multi-scenario formulation that assists the voltage regulation planning of a distribution network, making not only the traditional adjustments of voltage regulators, but also of the distribution transformers taps (DT) that simultaneously satisfy different configurations of load and DG power injections (that depends on the solar incidence, for example) during a typical day.The adjustments proposed in this article considered a large insertion of photovoltaic (PV) generation, which required careful monitoring to not exceed operational limits of the network and equipment. Therefore, to address these questions, it was necessary to act on the step voltage regulators and on the distribution transformers taps that existed along the feeders to control the voltage profile.To do this, the purpose of this article was to propose an optimization problem that applies to a three-phase unbalanced network (besides the conventional control actions, such as voltage regulator taps, as [2]) and DT tap adjustments to monitor the voltage profile, considering not only one point of operation, but a combination of multiple scenarios simultaneously (MTOPF). The consideration of multiple periods (or scenarios) must be made because after the DTs taps are fixed at planned positions, they do not change during the operation time. So, this tap allocation satisfies different conditions of load and DG penetrations (with pre-establishment of a different combination of scenarios) while minimizing the total electrical losses.Besides the description of the MTOPF proposed, some variations of this main idea were developed in a way to validate its results. We also proposed a parametrization of loads and GD insertions that allowed the execution of each scenario individually. This formulation was named PTOPF, and it can confront the results of a single-period f...

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